Brakes on 93 chevy van locking up

I'm gonna say check both front brake lines going to caliper they are known to collapse, loosen and hit brakes no fluid or a trickle and you've found the problem.

check the alocation bar under the master cyc if the censeror is out it will tell the brain to lock the wheels till it gets fixed. its part of the anti-lock system but when it goes it locks

our dealer mechanic checked my van and said the brake pump modulator valve is stuck open. he said it was actually the anti-skid spring inside the valve. unfortunately, we haven't been able to locate a valve (today) for a 93 G30. we will keep looking. until then, mechanic is saying don't drive it because the brakes could go any time!